﻿182 
  T. 
  E. 
  Savage 
  — 
  Devonian 
  Formation 
  of 
  Illinois. 
  

  

  the 
  early 
  upper 
  Devonian 
  (Tully) 
  limestone 
  of 
  the 
  New 
  

   York 
  section. 
  

  

  The 
  Winnipeg 
  osan 
  dolomite 
  in 
  the 
  Lake 
  Winnipeg 
  

   region, 
  containing 
  String 
  ocephalus 
  burtoni, 
  is 
  probably 
  

   the 
  youngest 
  Middle 
  Devonian 
  formation 
  in 
  the 
  Interior 
  

   Continental 
  province. 
  The 
  overlying 
  Man-it 
  oh 
  an 
  lime- 
  

   stone 
  in 
  that 
  region, 
  and 
  the 
  Abitibi 
  River 
  limestone 
  in 
  

   the 
  James 
  Bay 
  region, 
  are 
  thought 
  to 
  about 
  correspond 
  

   in 
  age 
  to 
  the 
  Wapsipinicon 
  and 
  Cedar 
  Valley 
  limestones 
  

   of 
  Iowa 
  and 
  Illinois, 
  and 
  would 
  thus 
  also 
  seem' 
  to 
  be 
  of 
  

   early 
  Upper 
  Devonian 
  age. 
  

  

  Sweetland 
  Creek 
  Shale. 
  — 
  The 
  Sweetland 
  Creek 
  shale 
  

   is 
  a 
  dark, 
  rather 
  thin-bedded 
  shale, 
  not 
  so 
  hard 
  or 
  black, 
  

   or 
  so 
  distinctly 
  laminated 
  as 
  the 
  Mountain 
  Glen 
  shale 
  

   in 
  southern 
  Illinois, 
  or 
  the 
  New 
  Albany 
  shale 
  in 
  Indiana. 
  

   It 
  contains 
  shells 
  of 
  a 
  small 
  linguloid, 
  and 
  great 
  num- 
  

   bers 
  of 
  spores 
  known 
  as 
  Sporangites 
  liuronensis, 
  which 
  

   appear 
  to 
  be 
  identical 
  with 
  those 
  occurring 
  in 
  the 
  Moun- 
  

   tain 
  Glen 
  shale 
  in 
  southern 
  Illinois, 
  with 
  which 
  formation 
  

   it 
  may 
  nearly 
  correspond 
  in 
  age. 
  The 
  Sweetland 
  Creek 
  

   shale 
  represents 
  a 
  northern 
  sea 
  invasion. 
  It 
  uncon- 
  

   formably 
  overlies 
  some 
  horizon 
  of 
  the 
  Cedar 
  Valley 
  

   limestone 
  or 
  older 
  rocks, 
  in 
  places, 
  as 
  in 
  the 
  vicinity 
  of 
  

   Chicago, 
  resting 
  on 
  strata 
  as 
  old 
  as 
  the 
  Niagaran 
  lime- 
  

   stone. 
  This 
  shale 
  ranges 
  from 
  50 
  to 
  200 
  feet 
  thick. 
  It 
  

   has 
  usually 
  been 
  considered 
  of 
  Upper 
  Devonian 
  age, 
  but 
  

   may 
  possibly, 
  as 
  Ulrich 
  thinks, 
  be 
  as 
  young 
  as 
  early 
  

   Mississippian. 
  It 
  may 
  be. 
  slightly 
  younger 
  than 
  the 
  

   Mountain 
  Glen 
  shale 
  in 
  the 
  southern 
  part 
  of 
  the 
  state; 
  

   and 
  younger 
  also 
  than 
  the 
  State 
  Quarry 
  limestone 
  and 
  

   Lime 
  Creek 
  shale 
  of 
  Iowa. 
  The 
  two 
  latter 
  formations 
  

   are 
  younger 
  than 
  the 
  Cedar 
  Valley 
  limestone 
  but 
  are 
  

   not 
  known 
  to 
  be 
  represented 
  by 
  rocks 
  in 
  Illinois. 
  

  

  University 
  of 
  Illinois, 
  Urbana, 
  111. 
  

  

  